Screening apparatus



Aug. 17, 1965 A. F. JONES SCREENING APPARATUS Filed May 51, 1962 2 Sheets-Sheet 1 1965 A. F. JONES 3,200,946

S CREENING APPARATUS Filed May 51, 1962 2 Sheets$heet 2 United States Patent Ofiice 3,200,946 SCREENING APPARATUS Alexander Forsyth Jones, Surbiton, Surrey, England, as-

signor of one-half to Ross Engineers Ltd., Surbiton, England Filed May 31, 1962, Ser. No. 199,162 Claims priority, application Great Britain, June 15, 1961, 21,607/61 4 Claims. (Cl. 209-106) This invention relates to screening apparatus of the kind comprising spaced parallel screening members over which the material to be screened moves in a direction transverse to the screening members such as is described in prior British Letters Patent Nos. 678,801 and 376,273.

The screening apparatus described in British Patent No. 376,273 was found in practice to be not entirely satisfactory because of material wedging between the rolls and because the means of varying the size of the apertures between the rolls was cumbersome and complex. The screening apparatus described in British Patent No. 678,801 was an improved construction which avoided these disadvantages by mounting the front roughened or ribbed member so as to be easily and controllably variable in distance from the rear screening member and having an inter-connecting member chain drive adapted to adjust itself automatically for any positions of the screening members relative to each other.

This screening apparatus has been found to suffer in turn from two disadvantages. Firstly, since the rear or smooth screening member is fixed in position and the front roughened or ribbed screening member is variable in position it is not a practical proposition to drive the front roll directly and it is convenient to couple the drive to the rear roll and transmit it to the front roll by a chain drive. liberately to give it the maximum frictional grip with the material and has to lift and clear the oversize material from the aperture it consumes the greater part of the power required to drive the screening apparatus. Thus the rear roll components and inter-roll chain drive has to be unduly heavy to transmit the required power to the front roll.

Secondly, to make the heavy chain drive automatically adjustable for any position of the screening members relative to each other it is formed into a loop by jockey sprockets which require mounting above the main frame of the machine, this requires a heavy and expensive structure which makes access to the machine difficult and which requires to be dismantled every time a screening member has to be replaced.

The object of the present invention is to provide an improved construction which will be free from the disadvantages above noted and the invention accordingly consists in screening apparatus of the kind referred to having the rear smooth screening member mounted so as to be easily and controllably variable in distance from the front roughened or longitudinally ribbed screening member and having an inter-screening member chain drive having fixed distances between centres irrespective of the relative positions of the screening members. (The words front and rear are used throughout in the sense given them in British Patent No. 678,801.)

According to a feature of the invention the inter-screening member chain drive is lightly loaded and adapted to adjust itself automatically for any positions of the screening members relative to each other, and is arranged to work on sprockets and shafts mounted directly on the main frame and screening members without the necessity of sprockets carried on a supperstructure.

Preferably the final stage of chain drive to the rear screening member is driven by a sprocket mounted on the Since the front roll is roughened or ribbed de-' axis of the pivot of the rear screening member so that the rear screening member can pivot without altering the centres of the final chain drive.

The invention also consisting other details and arrangements hereinafter described or indicated.

A preferred method of carrying the invention into effect will now be described with reference to the accompanying drawings, in which:

FIGURE 1 is a side elevation showing one convenient form of apparatus constructed in accordance with the invention;

FIGURE 2 is a front elevation;

FIGURE 3 is the other side elevation with the driving gear set removed for clarity; and

FIGURE 4 is a plan.

In carrying the invention into effect in one convenient manner the rear screening member or roll a is pivotally movable about the axis of shaft 1) to which it is rigidly located at either side of the machine by the arms 0 keyed to the shaft 11 and incorporating bearings for the roll a. Thus the roll a is free to rotate about its own axis and also to pivot to a required extent about the axis of shaft b and a pivoting of one end of the roll a is transmitted to the other end by shaft b so that the Whole rollpivots and maintains its parallel relationship to the front roll d.

One of the arms 0 is extended to provide a lever arm 0 through which the pivoting of the roll a can be controlled, a convenient control apparatus e described in prior patent specification No. 678,801 permits movement ofthe rear roll closer to or further from the front roll by turning ahandwheel e. Momentary movement of the rear roll away from the front roll to clear a jam and avoid damage to the machine is also permitted, as described in patent specification No. 67 8,801 and the roll is positively returned to its set position, firstly by the weight of the roll and secondly by the force of the compressed spring in the device described in prior patent specification No. 678,801 but not as described in said patent specification by reaction with the material as the rear roll is smooth and has the minimum of frictional grip with the material.

The drive to the machine from a motor worm gear set 1 or other convenient prime mover is connected direct to the fixed and roughened or longitudinally ribbed front roll d which can be rotated about its own axis by virtue of being mounted in bearings. As the front roll is roughened or ribbed to give the maximum frictional grip with the material it lifts and removes the oversize material from the aperture and carries it over the machine and in so doing most of the power is absorbed leaving only a small amount, estimated at a maximum of one third of the total power, to be transmitted to the rear roll which is smooth and not in severe frictional contact with the material. A chain drive g runs from the front roll d to one set of teeth on a double sprocket h which is bushed and free to rotate on an extension of the pivot shaft b. Another chain drive i runs from the other row of teeth on the double sprocket h to a sprocket keyed to the end of roll a. Thus rear roll a is driven in the same direction of rotation as front roll d and the relative speeds of rotation of the two rolls can be adjusted by the con ventional means of varying the number of teeth on the various sprockets. Chain drives g and i are of fixed cen-' tres but pivot movement of the rear roll a about the shaft b is permitted as chain drive i is also pivoted about the shaft b by virtue of the bushed double sprocket h being mounted and free to rotate on shaft 1;. Notwithstanding that the chain drives are of fixed. centres conventional jockey sprockets may be mounted on the slack sides of the chains to compensate for wear or improve the tooth contact or for other usual reasons. Because the rear roll a is of smooth and comparatively friction- Fatented Aug. 17, 1965 less construction alterations in peripheral speed due to pivoting of the roll about shaft b are not transmitted to the chain drives as shock loads nor do the chain drives have to transmit shock loads associated with the roughened or ribbed characteristics of the front roll impacting with the material.

I claim:

1. A screening apparatus including a first smooth roll, a second roll parallel to the first roll, the second roll being provided with a roughened or longitudinally ribbed periphery, fixed bearings supporting the second roll, a pair of resiliently mounted pivotable arms supporting the first roll, driving means for rotating the second roll, a first chain sprocket rigidly connected to the second roll, a second chain sprocket coaxial with the pivot axis of the arms, the second sprocket being a double sprocket, a drive chain interconnecting the first and second sprockets for rotating them in the same direction, a third chain sprocket rigidly connected to the first roll, and a driven chain interconnecting the second and third sprockets for rotating them in the same direction whereby the material to be screened is fed onto the first smooth roll and carried toward the second roll so that due to the roughened or longitudinally ribbed periphery of the second roll oversized particles are lifted by the frictional grip exerted by such periphery.

2. A screening apparatus including a frame, a first smooth roll, a parallel second roll said second roll being provided with a roughened or longitudinally ribbed periphery, first bearings fixed in the frame and supporting the second roll, two parallel resiliently mounted arms pivotable about a common axis, second bearings fixed in the frame and supporting the arms, bearings in the arms and supporting the first roll, driving means for rotating the second roll, a first chain sprocket rigidly connected to the second roll a second chain sprocket coaxial with the said common axis, a drive chain interconnecting the first and second sprockets for rotating them in the same direction, the second sprocket being a double sprocket, a third chain sprocket rigidly connected to the first roll, and a drive chain interconnecting the second and third sprockets for rotating them in the same direction where by the material to be screened is fed onto the first smooth roll and carried toward the second roll so that due to the roughened or longitudinally ribbed periphery of the second roll oversized particles are lifted by the frictional grip exerted by such periphery.

3. A screening apparatus as claimed in claim 2, and including a rotatable shaft mounted in the said second bearings and parallel to the said rolls, the arms being mounted fast on the shaft and the second chain sprocket being disposed on and free to rotate on the shaft.

4. A screening apparatus as claimed in claim 2, in which one of the arms is extended beyond the shaft, and including an adjustable resiliently loaded screw and nut device resiliently coupling the extended part of the said one of the arms to the frame and permitting limited separation of the rolls against the resilience of the said device.

References Cited by the Examiner UNITED STATES PATENTS 2,826,300 3/58 Ross 209-l06 2,901,048 8/59 Krukowski 209--107 X FOREIGN PATENTS 533,907 12/54 Belgium.

ROBERT B. REEVES, Primary Examiner.

ABRAHAM BERLIN, SAMUEL F. COLEMAN,

Examiners. 

1. A SCREENING APPARATUS INCLUDING A FIRST SMOOTH ROLL, A SECOND ROLL PARALLEL TO THE FIRST ROLL, THE SECOND ROLL BEING PROVIDED WITH A ROUGHENED OR LONGITUDINALLY RIBBED PERIPHERY, FIXED BEARINGS SUPPORTING THE SECOND ROLL, A PAIR OF RESILIENTLY MOUNTED PIVOTABLE ARMS SUPPORTING THE FIRST ROLL, DRIVING MEANS FOR ROTATING THE SECOND ROLL, A FIRST CHAIN SPROCKET RIGIDLY CONNECTED TO THE SECOND ROLL, A SECOND CHAIN SPROCKET COAXIAL WITH THE PIVOT AXIS OF THE ARMS, THE SECOND SPROCKET BEING A DDOUBLE SPROCKET, A DRIVE CHAIN INTERCONNECTING THE FIRST AND SECOND SPROCKETS FOR ROTATING THEM IN THE SAME DIRECTION, A THIRD CHAIN SPROCKET RIGIDLY CONNECTED TO THE FIRST ROLL, AND A DRIVEN CHAIN INTERCONNECTING THE SECOND AND THIRD SPROCKETS FOR ROTATING THEM IN THE SAME DIRECTION WHEREBY THE MATERIAL TO BE SCREENED IS FED ONTO THE FIRST SMOOTH ROLL AND CARRIED TOWARD THE SECOND ROLL SO THAT DUE TO THE ROUGHENED OF LONGITUDINALLY RIBBED PERIPHERY OF THE SECOND ROLL OVERSIZED PARTICLES ARE LIFTED BY THE FRICTIONAL GRIP EXERTED BY SUCH PERIPHERY. 